Emergent integration of the amine scrubbing method into photocatalytic CO2 reduction.

Developing strategies for photocatalytic reduction of low-concentration CO2 under ambient conditions is essential for mitigating global warming and addressing energy and carbon resource shortages. The amine scrubbing method (ASM), which captures dilute CO2 as carbamic acid using low-cost primary and secondary amines, is widely employed to generate concentrated CO2. However, releasing CO2 from carbamic acid to generate highly concentrated CO2 requires high-temperature heating, resulting in substantial energy consumption and cost. Herein, we report the integration of ASM with photocatalytic CO2 reduction. A newly synthesized complex [Ru(bpy)(P-P)(CO)(H)]+ (Ru-H+; bpy = 2,2'-bipyridine, P-P = Ph2PC2H4PPh2) serves as an efficient catalyst for reducing CO2 at low concentrations, even below 0.34%, in the presence of an Ir-based photosensitizer and a reductant (TONHCOOH ≥ 1925, Φ HCOOH = 39%, selectivityHCOOH > 97%). This system quantitatively converts CO2 captured by amines such as monoethanolamine into formic acid at room temperature. In this process, CO2 released from carbamic acid in solution is rapidly consumed via photocatalytic reduction, enabling efficient utilization of low-concentration CO2 without requiring energy-intensive regeneration processes.